Top MCQs on Sorting Algorithms with Answers

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Question 1

What is recurrence for worst case of QuickSort and what is the time complexity in Worst case?

  • Recurrence is T(n) = T(n-2) + O(n) and time complexity is O(n^2)

  • Recurrence is T(n) = T(n-1) + O(n) and time complexity is O(n^2)

  • Recurrence is T(n) = 2T(n/2) + O(n) and time complexity is O(nLogn)

  • Recurrence is T(n) = T(n/10) + T(9n/10) + O(n) and time complexity is O(nLogn)

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Question 2

Suppose we have an O(n) time algorithm that finds the median of an unsorted array. Now consider a QuickSort implementation where we first find the median using the above algorithm, then use the median as a pivot. What will be the worst-case time complexity of this modified QuickSort?

  • O(n^2 Logn)

  • O(n^2)

  • O(n Logn Logn)

  • O(nLogn)

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Question 3

Which of the following is not a stable sorting algorithm in its typical implementation.

  • Insertion Sort

  • Merge Sort

  • Quick Sort

  • Bubble Sort

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Question 4

Which of the following sorting algorithms in its typical implementation gives best performance when applied on an array which is sorted or almost sorted (maximum 1 or two elements are misplaced).

  • Quick Sort

  • Heap Sort

  • Merge Sort

  • Insertion Sort

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Question 5

Suppose we are sorting an array of eight integers using quicksort, and we have just finished the first partitioning with the array looking like this: 

2  5  1  7  9  12  11  10


Which statement is correct?

  • The pivot could be either the 7 or the 9.

  • The pivot could be the 7, but it is not the 9

  • The pivot is not the 7, but it could be the 9

  • Neither the 7 nor the 9 is the pivot.

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Question 6

Suppose we are sorting an array of eight integers using heapsort, and we have just finished some heapify (either maxheapify or minheapify) operations. The array now looks like this: 16 14 15 10 12 27 28 How many heapify operations have been performed on root of heap?

  • 1

  • 2

  • 3 or 4

  • 5 or 6

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Question 7

What is the best time complexity of bubble sort(optimised)?

  • N^2

  • NlogN

  • N

  • N(logN)^2

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Question 8

You have to sort 1 GB of data with only 100 MB of available main memory. Which sorting technique will be most appropriate?
  • Heap sort
  • Merge sort
  • Quick sort
  • Insertion sort
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Question 9

In a modified merge sort, the input array is splitted at a position one-third of the length(N) of the array. Which of the following is the tightest upper bound on time complexity of this modified Merge Sort.

  • N(logN base 3)

  • N(logN base 2/3)

  • N(logN base 1/3)

  • N(logN base 3/2)

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Question 10

Which sorting algorithm will take least time when all elements of input array are identical? Consider typical implementations of sorting algorithms.

  • Insertion Sort

  • Heap Sort

  • Merge Sort

  • Selection Sort

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